Jogging is a popular exercise, but it is known that the jogger's knees suffer from significant impact especially at the moment that his/her foot contacts the ground. The knees are injured after suffering from the frequent impacts for a period of time. Therefore, many exercisers such as elliptical exercisers, stepper, and air walker are developed to guide the user's feet to move along a trajectory which is similar to that of real jogging, such that the user's knees are protected from being impacted and injured.
One conventional elliptical exerciser is disclosed in U.S. Pat. No. 6,090,013 entitled “CROSS TRAINER EXERCISE APPARATUS”, which comprises a framework, two handles, a flywheel and two foot support members, wherein the flywheel and the handles are pivotally connected to the framework, and the foot support members are pivotally connected to two sides of the flywheel. When the handles are pivotally moved, the foot support members are guided by the flywheel and moved along a pedal trajectory which comprises a supporting travel and a crossing travel.
However, the pedal trajectory provided by the conventional elliptical exerciser is a very elliptical trajectory, so that the pedal travels on two sides of the flywheel have 180 degrees of timing delay. The timing of pedal trajectory is quite different from the one of real jogging.
Specifically, the cranks, or the flywheels, on two sides of the conventional elliptical exercisers have 180 degrees of phase difference, so that when one of the user's legs is at the front end of a pedal trajectory and going to support the user's weight, the other one is at the rear end of the pedal trajectory. As shown in FIG. 7, the supporting travel A1 and the crossing travel A2 of the pedal trajectory A have the same path length. However, in real jogging, when one of the user's legs is at the front end of the trajectory and going to support the user's weight, the other one not yet reaches the rear end of the trajectory but keeps moving backward, and does not lift to move forward until reaches the rear end of the trajectory. As shown in FIG. 8, in a trajectory B of real jogging, the path length of the supporting travel B1 is less than that of the crossing travel B2. The conventional elliptical exerciser cannot provide the user with the real jogging exercising mode and does not meet the principles of ergonomics.
When using the conventional elliptical exercisers, the user has to make his/her gait to be cooperated with the pedal trajectory provided by the conventional elliptical exerciser, so that the user cannot shift his/her weight from one leg to the other leg until his/her two legs both reach their respective extreme positions. The accumulation of the muscles sore and pain may cause sport injury to the user, and even worse if the user does not tread the pedals at a correct angle.
The present invention intends to provide an elliptical exerciser with a timing adjustment wheel so as to perform as real jogging action.